You could try a 1000mA wall wart, if you aren't using the Omega box for much, such as not using it drive headphones at full volume or something. There is a reasonable chance it might work. If anything, it might heat up the wall wart and cause the wall wart output voltage to drop below 9v. At least it should not damage the Omega box so long as the wall wart output is rated for 9VAC.
